linux-kernel - Re: [PATCH 1/2] tracing: kprobes: Prohibit probing on notrace functions

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Date:   Thu, 12 Jul 2018 17:49:52 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Francis Deslauriers <francis.deslauriers@...icios.com>
Cc:     mhiramat@...nel.org, peterz@...radead.org,
        mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] tracing: kprobes: Prohibit probing on notrace
 functions

On Thu, 12 Jul 2018 13:54:12 -0400
Francis Deslauriers <francis.deslauriers@...icios.com> wrote:

> From: Masami Hiramatsu <mhiramat@...nel.org>
> 
> Prohibit kprobe-events probing on notrace function.
> Since probing on the notrace function can cause recursive
> event call. In most case those are just skipped, but
> in some case it falls into infinite recursive call.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Tested-by: Francis Deslauriers <francis.deslauriers@...icios.com>

BTW, since you are sending the patch, you must also put in your
Signed-off-by too, after Masami's. You can keep the Tested-by.

-- Steve

> ---
>  kernel/trace/trace_kprobe.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index daa8157..952dc2a 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -487,6 +487,23 @@ disable_trace_kprobe(struct trace_kprobe *tk, struct trace_event_file *file)
>  	return ret;
>  }
>  
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> +static bool within_notrace_func(struct trace_kprobe *tk)
> +{
> +	unsigned long offset, size, addr;
> +
> +	addr = kallsyms_lookup_name(trace_kprobe_symbol(tk));
> +	addr += trace_kprobe_offset(tk);
> +
> +	if (!kallsyms_lookup_size_offset(addr, &size, &offset))
> +		return true;	/* Out of range. */
> +
> +	return !ftrace_location_range(addr - offset, addr - offset + size);
> +}
> +#else
> +#define within_notrace_func(tk)	(false)
> +#endif
> +
>  /* Internal register function - just handle k*probes and flags */
>  static int __register_trace_kprobe(struct trace_kprobe *tk)
>  {
> @@ -495,6 +512,12 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
>  	if (trace_probe_is_registered(&tk->tp))
>  		return -EINVAL;
>  
> +	if (within_notrace_func(tk)) {
> +		pr_warn("Could not probe notrace function %s\n",
> +			trace_kprobe_symbol(tk));
> +		return -EINVAL;
> +	}
> +
>  	for (i = 0; i < tk->tp.nr_args; i++)
>  		traceprobe_update_arg(&tk->tp.args[i]);
>